Any idea how to fix this? I can't find the good old "Software Sources", the Software Center is no help, and peeking at /etc/apt/sources.list, there's no mention of these PPAs anywhere, just the stock Ubuntu sources.

cat /etc/apt/sources.list.d/google-chrome.list ### THIS FILE IS AUTOMATICALLY CONFIGURED ###
# You may comment out this entry, but any other modifications may be lost.
deb http://dl.google.com/linux/chrome/deb/ stable main

Commented out the line as follows and now seems to work okay:
cat /etc/apt/sources.list.d/google-chrome.list
### THIS FILE IS AUTOMATICALLY CONFIGURED ###
# You may comment out this entry, but any other modifications may be lost.#deb http://dl.google.com/linux/chrome/deb/ stable main